Selective construction of spiro[indoline-3,5′-pyrrolo[3,4-b]azepines] and spiro[indoline-3,3′-pyrroles] via a [4 + 3]/[3 + 2] cycloaddition reaction of α,β-unsaturated aldimines and MBH adducts of isatins

Abstract

An efficient synthetic protocol for the selective construction of spiro[indoline-3,5′-pyrrolo[3,4-b]azepines] and spiro[indoline-3,3′-pyrroles] via a cycloaddition reaction of α,β-unsaturated aldimines and MBH adducts of isatins was successfully developed. DABCO facilitated the cycloaddition of α,β-unsaturated N-arylaldimines and MBH maleimides of isatins, affording spiro[indoline-3,5′-pyrrolo[3,4-b]azepines] with high yields and diastereoselectivity via a [4 + 3] cycloaddition process. On the other hand, the annulation reaction of α,β-unsaturated N-arylaldimines and MBH acrylates or nitriles of isatins resulted in spiro[indoline-3,3′-pyrroles] through a [3 + 2] cycloaddition process.